So you can think Vox Populi as a collection of mods (as it was before the 2.0 merge), compromising several submods: CP (Community Patch), CBO (Community Balance Overhaul), CSD (City-State Diplomacy), C4DF (Civilization 4 Diplomacy Features) and More Luxuries.
Community Patch is built upon William Howard's VMC (Various Mod Components), its main function is to provide bugfixes, AI optimizations and mod frameworks to provide tools for modders. It makes only a few gameplay changes, iirc the only one that really matters is the removal of "must set up before range attack" from siege units to help the AI. It also enabled some of WHoward's picknmix
mods by default.
CBO (by Gazebo, ilteroi and many contributors) is/was the main component of VP, adds new mechanics such as Local Happiness, Corporations&Monopolies and totally overhauls the game with new units, policies, wonders, traits.
CSD (by Gazebo) reworks CS influence system to be based on newly-added diplomacy units (emissaries etc.), adding new diplomacy buildings etc.
C4DF (by Putmalk) added new diplomacy features, most importantly vassalization.
More Luxuries (by Barathor) adds new luxuries, which CBO includes in corporations.
When the project first started it was modular, as in CBO could be used with/without any of the submods, also with many customization options to enable certain features of CBO separately (like unit rebalance, wonder rebalance etc.). Yet, in time, it became harder to maintain modularity, as new mechanics&balance required CBO to absorb the submods (ex: corporations needed to include more luxuries, wonders&new traits required CSD) and the majority played with all submods activated anyway. Before 2.0 these submods still existed in separate folders and in theory you could enable/disable them (and customization of CBO was still possible before 1.3 iirc), but this would lead to a pretty broken game and wasn't supported by maintainers. As of now, VP is one DLC sized mod, some limited customization from CBO still remains (ex. wonder consolidation prizes), but customization is left to modmods, which VP provides a generous framework for.
As someone who has been following the forums for a couple of years this is what I know about CP/CBO/VP, hope I didn't make any mistakes. Many of the other acronyms you listed come from JFD's mods, there was this wiki
for them but I'm not sure if it's up to date. I honestly don't know what state they are in, but anything other than Cultural Diversity is probably incompatible with VP.